Cold set composition for ceramic bodies

ABSTRACT

Disclosed are ceramic articles comprising ceramic honeycomb bodies and an aqueous composition, for example in the form of a cold-set plug, as well as processes for preparing ceramic articles and processes for making an aqueous composition for use with ceramic articles, for example as a cold-set plug composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/307,876 filed on Nov. 30, 2011, the content of which is relied uponand incorporated herein by reference in its entirety, and the benefit ofpriority under 35 U.S.C. §120 is hereby claimed.

TECHNICAL FIELD

The disclosure relates to honeycomb ceramic bodies and methods of makingthe same. In various embodiments, the disclosure relates to firedceramic honeycomb bodies comprising an unfired aqueous composition, forexample in the form of a cold-set plug. In further embodiments, thedisclosure relates to processes for preparing fired ceramic honeycombbodies, comprising applying an unfired aqueous composition, as well asprocesses for making an unfired aqueous composition for use with firedhoneycomb ceramic bodies, for example as a cold-set plug composition.

BACKGROUND

The production of honeycomb articles, such as, for example, dieselparticulate filters, often involves the application of ceramic cements(also referred to as pastes or sealants) onto pre-formed honeycombbodies. These cement compositions may be applied to the honeycomb body,for example to form plugs for the cell channels of the honeycomb, toform artificial skin (also known as “after-applied skin”), or to bondseveral smaller honeycomb segments together to make a larger honeycombbody.

Plugging of diesel particulate filters to force exhaust gas to flowthrough porous walls has historically been accomplished using one of twocomposition types. The first composition type is typically very similarto the raw material of the honeycomb body. For example, for a cordieritehoneycomb filter, the first composition may include clay and talc, andfiring to a temperature sufficient to convert the raw materials intocordierite. In various applications, this first composition typeprovides favorable rheology for plugging, due to the presence of clayand talc, which are platy raw materials (that is, flat and plate-likestructures found in soils) with high surface charge. The secondcomposition type may consist of pre-reacted, ground cordierite powderand both organic and inorganic binders. Without the inclusion of organicbinders, the second composition type does not exhibit sufficientplasticity. Thus, to achieve favorable rheology for plugging, the secondcomposition type is typically mixed with organic binder(s) (included forrheology) and then fired to about 1000° C. in order to remove thoseorganic components and react the inorganic binders (included forstructural strength after the organic components are burned off).

The second composition type has been modified to provide methods that donot require a firing process as described above. However, the secondcomposition type still presents some challenges for commercialization,particularly in view of the rheological behavior of the compositionwhich has been found to be prone to syneresis (that is, liquidseparation from solids). For example, when the second composition typeis used as a plugging application, the target plug depths often cannotbe achieved because batch liquids wick into the porous ceramic walls andthe cement dries out to a stiff state within a few millimeters. Althoughattempts have been made to modify the undesired behavior, to date thesuccess has been limited.

One such attempted solution to try to improve flow in a cement batch hasbeen to decrease particle size. However, decreasing particle size hasbeen found to increase the level of voids and dimples in the plugmaterial, which are typically considered undesirable for the pluggingapplication. Another attempted solution for improving plug depth hasbeen to increase the amounts of methylcellulose and/or water in thecement composition. However, this approach has also been found toincrease voids and dimples in the plug material. Thus, a need stillexists to find a composition, and method of making a composition thatwill exhibit acceptable rheology for application to ceramic honeycombbodies, such as for use as a plug composition, while reducing voids anddimples in the plug.

SUMMARY

Disclosed herein in various embodiments are methods of making an aqueouscomposition that may be useful for application to a ceramic honeycombbody, for example as a cold-set plug composition, comprising preparingan aqueous composition comprising a refractory filler, an inorganicbinder, and an organic binder, wherein the composition is not fired. Invarious embodiments, the refractory filler comprises particles having ad₅₀ ranging from about 10 μm to about 40 μm. In various exemplaryembodiments, certain methods may further comprise forming a cold-setplug from the composition. In further exemplary embodiments, the ceramichoneycomb body to which the composition may be applied may be a firedceramic honeycomb body.

Disclosed herein in further embodiments are methods of making a ceramicarticle, said methods comprising providing a ceramic honeycomb bodyhaving a plurality of cell channels, and applying an aqueous compositioncomprising a refractory filler, an inorganic binder, and an organicbinder to the ceramic honeycomb body, for example to the cell channels,wherein the aqueous composition is not fired before or after applicationto the ceramic honeycomb body. In various embodiments, the refractoryfiller comprises particles having a d₅₀ ranging from about 10 μm toabout 40 μm. In further exemplary embodiments, the ceramic honeycombbody to which the composition may be applied may be a fired ceramichoneycomb body.

Disclosed herein in yet further embodiments are ceramic articlescomprising a ceramic honeycomb body having a plurality of cell channelsand an unfired composition comprising a refractory filler, an inorganicbinder, and an organic binder. In various embodiments the refractoryfiller comprises particles having a d₅₀ ranging from about 10 μm toabout 40 μm. In various embodiments, the ceramic articles may beprovided wherein the unfired composition is in the form of a cold-setplug. In further exemplary embodiments, the ceramic honeycomb body maybe a fired ceramic honeycomb body.

Additional features and advantages of the invention will be set forth inthe detailed description which follows, and in part will be readilyapparent to those skilled in the art from the description or recognizedby practicing the invention as described herein, including the detaileddescription which follows, the claims, and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings are not intended to berestrictive of the invention as claimed, but rather are provided toillustrate exemplary embodiments of the invention and, together with thedescription, serve to explain the principles of the invention.

FIG. 1 is a graphic illustration showing plug depth achieved plottedagainst the percent level of methylcellulose (A4M Methocel) of twodifferent cordierite blends, 100% coarse cordierite and 50/50coarse/fine cordierite.

FIGS. 2A and 2B are photographic illustrations depicting plug qualityand depth for differing particle size distributions of 100% coarsecordierite (FIG. 2A) and 50/50 blend coarse/fine cordierite (FIG. 2B)and differing methylcellulose binder levels of 1.25% A4M Methocel (FIG.2A) and 1.50% A4M Methocel (FIG. 2B), with plug depth averaging about 5mm (FIG. 2A) and about 12.5 mm (FIG. 2B).

FIGS. 3A and 3B are photographic illustrations depicting plug qualityand depth for differing particle size distributions of 50/50 blendcoarse/fine cordierite (FIG. 3A) and 100% coarse cordierite (FIG. 3B),at the same methylcellulose binder levels of 1.50% A4M Methocel, withplug depth averaging about 12.5 mm (FIG. 3A) and about 6.18 mm (FIG.3B).

FIGS. 4A and 4B are photographic illustrations showing the typical plugquality for the same particle size distribution of 100% coarsecordierite at differing methylcellulose levels of 1.50% A4M Methocel(FIG. 4A) and 3.0% A4M Methocel (FIG. 4B), with plug depth averagingabout 6.8 mm (FIG. 4A) and about 13.3 mm (FIG. 4B).

DETAILED DESCRIPTION

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention as claimed. Other embodimentswill be apparent to those skilled in the art from consideration of thespecification and practice of the embodiments disclosed herein. It isintended that the specification and examples be considered as exemplaryonly, with the true scope and spirit of the invention being indicated bythe claims.

It is also to be understood that, while in various embodiments describedherein, steps of exemplary processes disclosed are recited in aparticular order, it is intended that the disclosed process steps may becarried out in any order that one of skill in the art would understandwould not significantly change the desired product.

Provided herein according to various embodiments are methods of makingan aqueous composition that may be useful for application to a ceramichoneycomb body, for example as a cold-set plug composition. Alsoprovided herein are methods of making a ceramic article, said methodscomprising providing a ceramic honeycomb body having a plurality of cellchannels and applying an aqueous composition, as well as ceramicarticles comprising an aqueous composition. In various exemplaryembodiments, the aqueous composition comprises at least one refractoryfiller, inorganic binder, and organic binder. In further exemplaryembodiments, the aqueous composition is not fired.

As stated above, the aqueous composition comprises at least onerefractory filler. In various embodiments, the at least one refractoryfiller comprises particles which are coarse. By “coarse,” it is meantthat the particles have a median particle size diameter, d₅₀ rangingfrom about 10 μm to about 40 μm, such as, for example, from about 15 μmto about 35 μm, from about 17 μm to about 25 μm, or from about 19 μm toabout 22 μm. In at least some embodiments, the particles of therefractory filler also have a d₁₀ greater than about 2 μm, such asgreater than about 3 μm, or greater than about 5 μm, and a d₉₀ less thanabout 110 μm.

The particles may be chosen from any particles known for makingcompositions for ceramic articles. By way of example, the particles ofthe refractory filler may be chosen from particles of cordierite, fusedsilica, silicates, silicon carbide, alumina, aluminum oxide, aluminumtitanate, titania, magnesium, magnesium stabilized alumina, calciumstabilized alumina, zirconia, zirconium oxide, zirconia stabilizedalumina, yttrium stabilized zirconia, calcium stabilized zirconia,zirconium mullite, mullite, spinel, magnesia, niobia, ceria, nitride,carbide, or any combination thereof.

The aqueous composition further comprises at least one inorganic binder.Any inorganic binder useful for making compositions for ceramic articlesmay be chosen. The inorganic binder may, in various embodiments, becolloidal, such as for example, colloidal silica. Other inorganicbinders that may be used include those that are known, such as, forexample, palygorskite, natural clay, bentonite, kaolin, or acellulose-based inorganic binder. Non-limiting inorganic bindersinclude, by way of example, colloidal silicas such as Ludox HS (HS-40Ludox®), AS, and SK, available from W.R. Grace & Company. In at leastcertain exemplary embodiments, the inorganic binder as-added to theaqueous composition is not gelled. By “not gelled” it is meant that aseparate and active gelling step is not undertaken, although it will beunderstood by those skilled in the art that some natural gelling mayoccur as the aqueous composition begins to dry.

The inorganic binder may be present in the aqueous composition as asuperaddition, and may be added in an amount ranging from about 5% toabout 20%, such as about 6% to about 16%, or about 7% to about 15%, byweight, relative to the total weight of the refractory filler in thecomposition.

In certain embodiments, the inorganic binder may contribute to themechanical or rheological properties of the aqueous composition, such asthe strength and viscosity of the composition, although this is not arequired property. The improved strength and viscosity can, for example,improve the ability to withstand further processing steps and aid inplugging selected ends of a honeycomb body.

The aqueous composition further comprises at least one organic binder.Any organic binder useful for making compositions for ceramic articlesmay be chosen. Non-limiting organic binders may include, for example,cellulose materials, such as, methylcellulose; a wide variety of gums,such as, for example, Xanthan gum and actigum, and polyvinyl alcohol andderivatives thereof. It is contemplated that other organic binders thatare known in the art may be suitable for use in the aqueous composition,such as, for example, hydroxypropylmethylcellulose, and othermethylcellulose derivatives, and/or any combinations thereof. Anexemplary methylcellulose binder is Methocel™ A4M, available from theDow Chemical Company of Midland, Mich., USA.

In certain exemplary embodiments, the organic binder may be present inthe aqueous composition as a superaddition, and may be added in anamount ranging from about 1.0% to about 5.0%, such as about 1.0% toabout 3.0%, by weight of the refractory filler in the composition. Incertain embodiments, the organic binder may be present in an amount ofabout 1.0%, such as about 2.0%, about 3.0%, about 4.0%, or about 5.0%,or more, by weight. It should be noted that other exemplary amountsin-between the given ranges, such as, for example, about 1.25%, about1.50%, about 1.75%, and so on, are contemplated as well.

In certain embodiments, the organic binder may contribute to therheological properties of the aqueous composition, such as the cohesionand plasticity of the composition, although this is not a requiredproperty. The improved cohesion and plasticity can, for example, improvethe ability to shape the aqueous composition and aid in pluggingselected ends of a honeycomb body.

Other components may optionally be added to the aqueous composition aswell, including those which may assist in the blending and preparationof the aqueous composition prior to use, e.g. as a cold-set plug orprior to application to a structure such as a honeycomb structure or afilter structure. For example, a liquid vehicle may be included in theaqueous composition to assist in achieving the desired rheologicalproperties. The liquid vehicle may be incorporated to provide a flowableor paste-like consistency to the aqueous compositions, for example, sothat the aqueous composition can be applied to a honeycomb body as apaste or cement. According to certain embodiments, the liquid vehiclecan be water, although it should be understood that other liquidvehicles exhibiting solvent action with respect to suitable organicbinders can be used.

The liquid vehicle may be present as a superaddition, and may be addedin an amount less than or equal to 60% by weight of the aqueouscomposition, and less than 40% by weight of the inorganic powder batchcomposition. In still other embodiments, the liquid vehicle is presentas a superaddition in an amount that does not exceed 35% by weight ofthe aqueous composition, including, for example, a superaddition amountof from 25% to 35% by weight of the aqueous composition. It will beunderstood by those skilled in the art that it is desirable to minimizethe amount of liquid vehicle while still obtaining a paste-likeconsistency capable of being forced into selected ends of a honeycombstructure. Minimization of liquid components in the aqueous compositionmay, in at least certain embodiments, lead to further reductions inundesired slumping, drying shrinkage, and crack formation during thedrying process of the plug application.

Optionally, other additives may also be included in the aqueouscomposition, for example to aid in processing before, during, or afterapplication to a honeycomb structure or in other forms of use, such as,by way of non-limiting example, pore formers.

To prepare the aqueous composition, the refractory filler, inorganicbinder, and organic binder may be mixed together by conventional means.The rheological properties may be measured and adjusted according to thedesired consistency, depending on the intended final application. Forexample, the rheology of the aqueous composition can further becontrolled by modifying the amount of a liquid vehicle in relation tothe viscosity of the organic binder. The liquid vehicle addition and theviscosity of the organic binder can be used to control the pluggingforces required to plug ceramic honeycomb structures with the disclosedaqueous compositions, as well as to minimize undesirable slump anddimple formation.

In certain exemplary embodiments, the aqueous composition can be formedas a cold-set composition, which may be used as a plugging compositionto plug one or more selected channels of a honeycomb body. The cold-setplug can be formed according to known procedures. According to variousembodiments, the aqueous composition is not fired before or after thecold-set composition is applied to the ceramic body and/or the plug isformed. Without wishing to be bound, it is believed that this ispossible due to the particular make-up of the composition, as describedherein. Specifically, the combination of coarser particle sizedistributions with an increased organic binder levels has been found topermit the composition to achieve a desired rheology while maintainingintegrity (e.g. for forming plugs for cell channels), without requiringa firing step.

In other embodiments, the disclosed aqueous composition is suitable foruse in forming an after-applied surface coating or skin on at least oneperipheral region of a honeycomb body or structure. Accordingly,portions of the outer surface of a formed honeycomb body can optionallybe removed by known methods such as sanding, grinding, and the like, inorder to obtain a resulting body having a desired shape. After theremoval of material from the peripheral portion of the body, thedisclosed aqueous composition can be applied to the peripheral portionor surface in order to form an after applied skin to the honeycomb bodyand to re-seal any honeycomb structure channels that may have beenexposed or breached due to the removal of material. Once the skincoating has been applied, the applied aqueous composition can be usedwithout firing, as described herein.

In still another embodiment, the disclosed composition can be applied assegment cement, for example to join two or more cellular honeycombbodies. In various embodiments, the segment cement can be used to jointwo or more honeycomb bodies lengthwise or in an end to endrelationship. Alternatively, the cements can be used to laterally jointwo or more cellular segments. For example, in some embodiments, it maybe desirable to join two or more cellular honeycomb segments togetherlaterally or in a side to side arrangement in order to form a largercellular or honeycomb structure that may be too large for extrusionforming techniques described above. Once the segment cement has beenapplied to a honeycomb and the desired number of cellular segments hasbeen joined, the segment composition can again used without firing asdescribed herein.

In another aspect, the disclosure provides ceramic articles, e.g.particulate filters, comprising a ceramic honeycomb body having aplurality of cell channels, and an aqueous composition, optionallyunfired, as well as methods for making ceramic articles. The methodscomprise steps of providing a ceramic honeycomb body, optionally fired,having a plurality of cell channels, and applying an aqueous compositionto the ceramic honeycomb body. The aqueous composition is as describedabove.

The fired ceramic honeycomb body can be chosen from those known and usedin the art. By way of non-limiting example, in a honeycomb structuredefining a plurality of cell channels bounded by porous cell channelwalls, at least a portion of the plurality of cell channels can includeplugs, wherein the plugs are formed from a cement composition, such asthe aqueous composition disclosed herein. To plug selected channels, thedisclosed aqueous composition can be forced into selected open cells ofa desired porous ceramic honeycomb structure in the desired pluggingpattern and to the desired depth, by one of several known pluggingprocess methods. For example, the plugging can be effectuated by using amasking apparatus and process such as that disclosed and described inU.S. Pat. No. 6,673,300, the wall flow configuration disclosed anddescribed in PCT Publication No. PCT/US2008/013009, and U.S. PublicationNo. 2009/0286041, incorporated by reference herein.

As can be seen from the above description, the disclosure solves atleast some of the problems previously encountered with plugging cellchannels of ceramic honeycomb bodies. The two conventional “knobs”identified for increasing plug depth capability are the addition of finecordierite and increasing organic binder, e.g. Methocel. Both of thesemethods have shown increased voids and dimpling of the plugs. However,through the use of 100% coarse cordierite, in addition to higher levelsof organic binder, e.g. Methocel, the desired plug depth, e.g. about 4mm to about 12 mm, and plug quality, e.g. substantially free of voidsand/or dimples, can be achieved.

The aqueous compositions described herein can exhibit advantageousrheological properties that render them well-suited for application toceramic honeycomb bodies, including, for example, for use in formingend-plugged porous ceramic wall flow filters. The coarser particle sizeand increased binder level, as compared to previously known and testedcement compositions, are, at least in part, surprisingly andunexpectedly believed to be responsible for the improved properties.Further, a narrow-particle-size distribution coarse filler also aids inthe prevention of voids and/or dimples. As a result, the aqueouscomposition enables cold-set plugs in the plug depth range of about 4 mmto about 12 mm, such as about 6 mm to about 10 mm. It should be noted,however, that plug depths outside these ranges are also possible, suchas, for example, a plug depth of about 14 mm or higher.

FIG. 1 is a graphic illustration showing the plug depth achieved plottedagainst the percent level of methylcellulose (A4M Methocel) of twodifferent cordierite blends, 100% coarse cordierite and 50/50coarse/fine cordierite. The 50/50 coarse/fine curve appears to plateauafter the 12 mm line; however, one of skill in the art will appreciatethat the slope of the curve would have been steeper if the 13 mm plugdepth was not the end-targeted plug depth to be measured.

FIGS. 2A and 2B are photographic illustrations depicting plug qualityfor differing particle size distributions of 100% coarse cordierite(FIG. 2A) and 50/50 blend coarse/fine cordierite (FIG. 2B) and differingmethylcellulose binder levels of 1.25% A4M Methocel (FIG. 2A) and 1.50%A4M Methocel (FIG. 2B), with plug depth averaging about 5 mm (FIG. 2A)and about 12.5 mm (FIG. 2B). The solid plugs (FIG. 2A) formed from anaqueous composition with 100% coarse cordierite and a methylcelluloselevel of 1.25% of A4M Methocel, have an average plug depth of about 5mm. The solid plugs (FIG. 2B) formed from an aqueous composition with50/50 coarse/fine cordierite and a methylcellulose level of 1.50% of A4MMethocel, have an average plug depth of about 12.5 mm, but exhibitdimpling. Dimples can be difficult to quantify so this is usually doneby visual comparison as shown in these figures. For example, there isvisibly less dimpling in FIG. 3A than in FIG. 3B. This corresponds tothe composition make-up, including the methylcellulose type and level aswell as the cordierite blend. Dimpling is believed to be due to thedrying of the part, such as the ceramic honeycomb body, and involvesshrinkage of the part. Thus, by increasing the particle size, theshrinkage can be decreased as well as the overall movement of thecomposition in the channel or pore, resulting in fewer dimples.

However, additional liquid vehicle or water can be added to adjust theviscosity of the organic binder and the consistency of the composition.This should be counterintuitive to those skilled in the art, who wouldexpect that these two properties would be coordinated and adjustedtogether to improve plug integrity and increase plug depth withfavorable rheology.

Thus, in FIGS. 3A and 3B the typical plug quality for differing particlesize distributions of 50/50 blend coarse/fine cordierite (FIG. 3A) and100% coarse cordierite (FIG. 3B), both at the same methylcellulose levelof 1.50% A4M Methocel is shown. By changing the 50/50 coarse/fine blendof cordierite to 100% coarse the dimples and voids are eliminated usingthe same 1.5% A4M Methocel as shown in the visual comparison betweenFIGS. 3A and 3B. Although the plug quality is much better with the 100%coarse cordierite, the plug depth capability is reduced by about half to6.18 mm (FIG. 3B). The average plug depth in FIG. 3A is about 12.5 mm.However, with the 100% coarse cordierite the A4M Methocel level can beincreased much more before dimples are seen. Unlike the 50/50 cordieriteblend that has a step change in plug depth capability, when plottedgraphically, the 100% coarse cordierite has a linear slope as theMethocel level is increased (as seen in the graph of FIG. 1 depictingthe plug depth achieved plotted against the percent level ofmethylcellulose (A4M Methocel) of 100% coarse cordierite).

The 100% coarse cordierite composition even at 3.0% A4M Methocel (FIG.4B) does not exhibit the heavy dimpling and voids that the 50/50 blendexhibited at 1.50% A4M Methocel (FIG. 4A), as depicted in FIGS. 4A and4B. The aqueous composition with 3.0% A4M Methocel also achieves theplug depth capability needed with the 100% coarse cordierite. Theachieved average plug depths depicted here are about 6.8 mm (FIG. 4A)and about 13.3 mm (FIG. 4B).

As used herein, the singular forms “a,” “an,” and “the” include pluralreferents unless specifically indicated to the contrary. Thus, forexample, reference to “a cold-set plug” includes embodiments having oneor more cold-set plugs.

As used herein, a “wt. %” or “weight percent” or “percent by weight” ofa component is based on the total weight of the aqueous composition inwhich the component is included, unless specifically stated to thecontrary (e.g. when the component is stated to be added as asuperaddition relative to the weight% of the refractory filler).

As used herein, “prevention of voids and/or dimples,” “prevent voidsand/or dimples,” and similar language, is intended to refer to plugs,coatings, and other applications of compositions formed according tovarious embodiments described herein, that have no, or substantially no,voids or dimples, or that have reduced occurrences of voids or dimplesrelative to plugs, coatings, and other applications of compositionsformed from previously known compositions.

As described herein, the particle diameters of all powders were measuredby a laser diffraction technique, using a Microtrac particle sizeanalyzer.

The values d₁₀ and d₅₀ are defined as the diameters at 10% and 50% ofthe cumulative particle size distribution, with d₁₀<d₅₀. Thus, d₅₀ isthe median particle diameter, and d₁₀ is the particle diameter at which10% of the particles are finer. The value of d₉₀ is the particlediameter for which 90% of the particles are finer in diameter; thusd₁₀<d₅₀<d₉₀.

As used herein, the terms “unfired,” “not fired,” and the like, meanthat the aqueous composition is not fired after it is prepared, eitherbefore or after application to the ceramic honeycomb body, including butnot limited to before or after a plug is formed.

As used herein with respect to the aqueous composition, the terms“apply,” “applied,” and the like, are meant to indicate that thecomposition is brought into contact with the ceramic body, such as, forexample, in a coating composition or by plugging the cells of thehoneycomb body with the composition. By way of example, the aqueouscompositions can be applied to honeycomb bodies as a plugging cementcomposition, segment cement, or even as an after-applied artificial skinor coating.

As used herein, “after-applied” skin or coating refers to a nonco-extruded skin or surface coating on a peripheral region of anextruded honeycomb body. For example, when honeycomb structures areextrusion formed, dried, and fired, the resulting body may need to beresized or shaped in order to comply with desired size and shapetolerances for a given end use application.

As used herein, a “superaddition” refers to a weight percent of acomponent, such as for example, an organic binder, liquid vehicle,additive, or pore former, based upon and relative to 100 weight percentof the aqueous composition.

As used herein, the term “optional” or “optionally” means that thesubsequently described event or circumstance mayor may not occur, andthat the description includes instances where said event or circumstanceoccurs and instances where it does not.

Unless otherwise indicated, all numbers used in the specification andclaims are to be understood as being modified in all instances by theterm “about,” whether or not so stated. By way of example, “100% coarsecordierite” is understood to include cordierite that is “about 100%coarse.” It should also be understood that the precise numerical valuesused in the specification and claims form additional embodiments of theinvention, and are intended to include any ranges which can be narrowedto any two end points disclosed within the exemplary values provided.Efforts have been made to ensure the accuracy of the numerical valuesdisclosed herein. Any measured numerical value, however, can inherentlycontain certain errors resulting from the standard deviation found inits respective measuring technique.

EXAMPLES

To further illustrate the principles of the disclosure, the followingexamples are set forth to provide those of ordinary skill in the artwith a complete disclosure and description of the aqueous composition,ceramic filter and the related methods. These examples are intended onlyto be exemplary and are not intended to limit the scope of theinvention. Unless otherwise indicated, parts are by weight, temperatureis ° C. or is at ambient temperature, and pressure is at or nearatmospheric.

The aqueous composition in the following examples was prepared andapplied to a porous ceramic honeycomb structure comprised of amicrocracked porous ceramic material. Exemplary amounts of the rawmaterials used to make the aqueous composition, as well as those of aknown control cement composition, are set for in Table 1 below.

TABLE 1 Inventive Control Ingredient Composition Composition Cordierite100% 50% Powder (Coarse) Cordierite 50% Powder (Fine) Colloidal 25 wt. %25 wt. % Silica* Organic 2.5 wt. %   1 wt. % Binder* Water* 33 wt. % 25wt. % *Indicates the weight percentage for the batch ingredient wascalculated as a superaddition relative to the combined total weight ofthe powdered cordierite.

The two compositions were then evaluated to determine the rheologicalbehavior and plug integrity based on substituting different cordieriteblends for the batch ingredients. Exemplary compositions with differentcordierite blends and the varying levels and types of organic bindersthat were used and evaluated are set forth in Table 2 below. Theresultant plug depths for each of the different combinations in theexemplary compositions are also recorded. As is evident by the collecteddata, the average plug depth is generally increased with the combinationof a higher methylcellulose level and a coarser particle sizedistribution is used.

TABLE 2 Methylcellulose Methylcellulose Cordierite Plug depthComposition Type Level Blend (average) PL289 A4M 1.00% 50/50 5.3 PC1 A4M2.00% 50/50 12.0 PC2 A4M 3.00% 50/50 13.2 PC6 A4M 1.00% 50/50 5.5 PC7A4M 2.00% 50/50 13.6 PC8 A4M 3.00% 50/50 13.2 CS25 A4M 1.50% 50/50 12.6CS27 A4M 1.50% 100 6.2 CS28 A4C 4.00% 100 11.0 CS29 A4C 3.50% 100 9.6CS30 A4C 3.25% 100 8.7 CS31 A4M 1.75% 100 7.5 CS32 A4M 3.00% 100 13.3CS33 F240 1.00% 100 6.1 CS34 F240 3.00% 100 14.0 CS35 A4M 2.00% 100 8.1CS36 A4M 2.50% 100 10.8 CS37 F240 2.00% 100 9.4 CS38 A4M 1.25% 50/50 5.0

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit and scope of the invention. Thus it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A ceramic article comprising: a fired ceramichoneycomb body having a plurality of cell channels; and an unfiredcomposition comprising a refractory filler, an inorganic binder, and anorganic binder; wherein the refractory filler comprises particles have ad₅₀ in the range from about 10 μm to about 40 μm and a d₉₀ less thanabout 110 μm.
 2. The ceramic article of claim 1, wherein the particlesof the refractory filler have a d10 greater than about 2 μm
 3. Theceramic article of claim 1, wherein the unfired composition is disposedin at least one cell channel of the fired ceramic honeycomb body in theform of at least one plug.
 4. The ceramic article of claim 3, whereinthe at least one plug has a depth in the cell channel ranging from about4 mm to about 12 mm.
 5. The ceramic article of claim 3, wherein the atleast one plug has a depth in the cell channel ranging from about 6 mmto about 10 mm.
 6. The ceramic article of claim 1, wherein the inorganicbinder is a colloidal silica that is present in an amount ranging fromabout 5% to about 20% by weight as a superaddition.
 7. The ceramicarticle of claim 1, wherein the organic binder is present in thecomposition in an amount ranging from about 1.0% to about 5.0% byweight.
 8. The ceramic article of claim 1, wherein the organic binder ischosen from methylcellulose, Xanthan gum, actigum, and polyvinylalcohol.
 9. The ceramic article of claim 1, wherein the organic bindercomprises methylcellulose.
 10. The ceramic article of claim 1, whereinthe particles of the refractory filler are chosen from particles ofcordierite, fused silica, silicates, silica carbide, alumina, aluminatitanate, mullite, zirconia, zirconia mullite, and spinel.
 11. A ceramicarticle comprising: a fired ceramic honeycomb body having a plurality ofcell channels; and at least one plug disposed in at least one cellchannel of the fired ceramic honeycomb body, the at least one plugcomprising a refractory filler, an inorganic binder, and an organicbinder; wherein the refractory filler comprises particles having a d₅₀in the range from about 10 μm to about 40 μm, and a d₉₀ less than about110 μm.
 12. The ceramic article of claim 11, wherein the particles ofthe refractory filler have a d10 greater than about 2 μm
 13. The ceramicarticle of claim 11, wherein the ceramic article comprises a pluralityof plugs.
 14. The ceramic article of claim 11, wherein the at least oneplug has a depth in the cell channel ranging from about 4 mm to about 12mm.
 15. The ceramic article of claim 11, wherein the at least one plughas a depth in the cell channel ranging from about 6 mm to about 10 mm.16. The ceramic article of claim 11, wherein the inorganic binder is acolloidal silica that is present in an amount ranging from about 5% toabout 20% by weight as a superaddition.
 17. The ceramic article of claim11, wherein the organic binder is present in the composition in anamount ranging from about 1.0% to about 5.0% by weight.
 18. The ceramicarticle of claim 11, wherein the organic binder is chosen frommethylcellulose, Xanthan gum, actigum, and polyvinyl alcohol.
 19. Theceramic article of claim 11, wherein the organic binder comprisesmethylcellulose.
 20. The ceramic article of claim 11, wherein theparticles of the refractory filler are chosen from particles ofcordierite, fused silica, silicates, silica carbide, alumina, aluminatitanate, mullite, zirconia, zirconia mullite, and spinel.